Seneca
SILVER Star
If the answer to this question is out there, I haven’t found it, so hopefully this isn’t a redundant post.
Short version
Will a 100 lbs motorcycle carrier, carrying a 400 lbs motorcycle (total weight 500 lbs), which is fully suspended by the standard 2”
hitch of an FZJ80 (itself with a 5000 lbs towing capacity and thus 500 lbs max tongue weight), which protrudes ~18” (posteriorly) beyond the standard offset of a ball joint, produce too much torque on the frame of the FZJ80? I suspect the answer is yes.
Long Version
FZJ80 has a max tow rating of 5000 lbs, which implies a 500 lbs max tongue weight (or 750 lbs if we can follow the 10%-15% rule of thumb?).
Attach a trailer to a standard ball joint, and yeah, make sure it has a 500 lbs (max) distributed on that ball joint.
But what if the ball protrudes 12” out farther than “standard?” That would add an additional 500 ft-lbs of torque on the frame (or attachment point of the hitch to the frame).
For a real world example, take a 600 lbs max load motorcycle carrier (which is fully supported by the hitch, rather than being a trailer). The carrier weighs 100 lbs itself, and a 400 lbs motorcycle is carried by it. The center of mass of the carrier with motorcycle protrudes about 20” out beyond the hitch attachment, or… ~18” beyond the same standard position of a ball joint.
Let’s assume the standard ball joint is 6” beyond the pivot point (at which the hitch and frame are bolted/welded/etc. together). With that, 500 lbs of perpendicular force applied to the ball joint results in 250 ft-lbs of torque on the frame (pivot point).
In the motorcycle carrier example, the moment arm on the frame is roughly 24” beyond the hitch-frame attachment point (pivot point), and thus loading it with 500 lbs (carrier + motorcycle) of perpendicular force applies 1000 ft-lbs of torque on the frame (4x the max torque we can infer from the max tongue weight).
I’m making quite a few oversimplifications/assumptions here, but either I’m overthinking it, or 99% of the people out there with motorcycle carriers are exceeding the torque rating (which I can’t find specified anywhere) of their frames (for any vehicle), assuming we can deduce the torque limit by closely estimating the pivot point on the frame and the moment arm produced by the carrier.
Too many notes?
Short version
Will a 100 lbs motorcycle carrier, carrying a 400 lbs motorcycle (total weight 500 lbs), which is fully suspended by the standard 2”
hitch of an FZJ80 (itself with a 5000 lbs towing capacity and thus 500 lbs max tongue weight), which protrudes ~18” (posteriorly) beyond the standard offset of a ball joint, produce too much torque on the frame of the FZJ80? I suspect the answer is yes.
Long Version
FZJ80 has a max tow rating of 5000 lbs, which implies a 500 lbs max tongue weight (or 750 lbs if we can follow the 10%-15% rule of thumb?).
Attach a trailer to a standard ball joint, and yeah, make sure it has a 500 lbs (max) distributed on that ball joint.
But what if the ball protrudes 12” out farther than “standard?” That would add an additional 500 ft-lbs of torque on the frame (or attachment point of the hitch to the frame).
For a real world example, take a 600 lbs max load motorcycle carrier (which is fully supported by the hitch, rather than being a trailer). The carrier weighs 100 lbs itself, and a 400 lbs motorcycle is carried by it. The center of mass of the carrier with motorcycle protrudes about 20” out beyond the hitch attachment, or… ~18” beyond the same standard position of a ball joint.
Let’s assume the standard ball joint is 6” beyond the pivot point (at which the hitch and frame are bolted/welded/etc. together). With that, 500 lbs of perpendicular force applied to the ball joint results in 250 ft-lbs of torque on the frame (pivot point).
In the motorcycle carrier example, the moment arm on the frame is roughly 24” beyond the hitch-frame attachment point (pivot point), and thus loading it with 500 lbs (carrier + motorcycle) of perpendicular force applies 1000 ft-lbs of torque on the frame (4x the max torque we can infer from the max tongue weight).
I’m making quite a few oversimplifications/assumptions here, but either I’m overthinking it, or 99% of the people out there with motorcycle carriers are exceeding the torque rating (which I can’t find specified anywhere) of their frames (for any vehicle), assuming we can deduce the torque limit by closely estimating the pivot point on the frame and the moment arm produced by the carrier.
Too many notes?
